NMR Relaxation Rates of Quadrupolar Aqueous Ions from Classical Molecular Dynamics Using Force-Field Specific Sternheimer Factors

The nuclear magnetic resonance (NMR) relaxation of quadrupolar nuclei is governed by the electric field gradient (EFG) fluctuations at their position. In classical molecular dynamics (MD), electron cloud contribution to EFG can be included via Sternheimer approximation, in which full nucleus that computed using quantum DFT considered proportional arising from external, charge distribution. this work, we systematically assess quality approximation as well impact force (FF) on NMR rates aqueous ions infinite dilution. particular, compare obtained an ab initio parametrized polarizable FF, a recently developed empirical FF with scaled ionic charges and simple non-polarizable formal charges. Surprisingly, all three FFs yield good values for smaller less solutes, provided model-specific parametrization employed. Yet, better estimates divalent more species. We find linear relationship between EFGs holds cases considered, however, such often leads quite large errors resulting variance, directly rate. attempted reduce including first order nonlinear corrections EFG, yet no clear improvement variance has been found. latter result indicates refined methods determining ion position, particular those take into account instantaneous atomic environment around ion, might necessary improve rate MD.